The invention is based on a fuel injection pump for supplying fuel to injection nozzles of self-igniting internal combustion engines. The pump comprises a housing means within which a bore and a suction chamber are defined. A pump piston is mounted for reciprocating movement within the bore as a function of engine rpm, the housing means and piston defining a pump work chamber in said bore. An intake connected to the suction chamber communicates with the work chamber through which fuel is delivered from the suction chamber to the work chamber. The reciprocating movement of the piston includes a compression stroke during which fuel is compressed to an injection pressure for discharge through a plurality of pressure lines, each of which is connected at one end to the housing means in communication with the work chamber and at its other end to an injection nozzle.
With fuel injection pumps for Diesel engines, a goal is to prolong the duration of injection during idling and at low partial load, so as to attain quieter idling. In a known fuel injection pump of this kind, fuel is directed simultaneously via the relief conduit and via the pressure lines during idling and low partial load, after the compression stroke of the pump piston has begun. However, before the fuel injection nozzles open, a higher pressure is temporarily established than that which will be required after opening for the further injection of relatively small injection quantities. This advance pressurization causes rpm-dependent variations in the actual onset of injection and also results in substantial, undesirable differences in the partial quantity flowing out. Furthermore, the partial quantity in this known pump flows into a withdrawal chamber, which functions similarly to a reservoir and thus exerts substantial influence on the course of injection, having the particular disadvantage that precise regulation of the injection quantity is made more difficult.